AUTO TECH AND ROAD SAFETY

Guide to Car Safety Systems

Guide to Car Safety Systems image

Text: Inigo S. Roces / Photos: AutoIndustriya.com, Mercedes-Benz Press, Toyota Press, Volvo | posted August 29, 2012 15:34

A guide to the many acronyms and jargons that help most in those critical seconds

New cars are truly technical wonders these days. They’re loaded with safety systems that keep a keener eye on the road than most drivers do. The average car already has quite a number of them, sprinkled over the brochure as gibberish and acronyms that add up to make an intimidating feature list. The chief villains are the acronyms, which, like any technical field are continuously updated and often made more complicated. So what do each of these features mean and do, follow the list below to find out.

1. ABS+EBD

Many of you may already know that ABS means Anti-lock Brake System, yet the reason why this is so vital is often forgotten. In a panic situation, the first reaction is usually to step on the brake. The problem is that stepping too hard can easily lock up the wheels, making the car feel like a sled on ice. Before it was fitted as standard, older drivers were trained to pump the brakes to prevent this from happening. Easier said than done in that kind of situation. With ABS, sensors are placed on all wheels with disc brakes, checking the brake pressure and relieving it if there is too much. This allows the driver to brake as hard as desired, leaving the computer to keep the pressure just short of a lock up.

Electronic Brake-force Distribution (EBD) is always found in tandem with ABS and never without it. It works with ABS to balance the pressure on the front and rear brakes. Most cars are front heavy, and when braking. As such, the wheels with a light load (behind) require less pressure to stop than the wheels with a heavy load (in front). At the same time, the weight of a car shifts during braking, complicating it even more. Simply put, an EBD system can not only detect how much weight is being supported by each wheel, but change the amount of braking power sent to each wheel on at any second. Without EBD, heavy vehicles are more likely to rotate or twist under braking, kind of like the trailer of a truck jack-knifing, because the rear wheels can’t stop as fast as the front.

ABS

Feels like…

ABS and EBD systems vary from brand to brand. Some emit vibrations in the wheel and pedal to let you know they’re working. Others are more subtle and hardly return vibration at all. The best indicator that they’re working is the sound. Rather than a long continuous screech, a working ABS+EBD system sounds like a series of short screeches or shudders (like a car rolling over rumble strips). This is the sound of the calipers locking the discs, letting go to let them roll and engaging again. Unlike other safety systems, indicator lights for ABS typically light up when there’s something wrong with it, not to show you it’s working.

What to do…

In a car equipped with ABS+EBD, brake as you normally would. Simply step on the pedal as hard as you can and the vehicle should do all the work for you. Do not pump the brakes. This only confuses the computer even more, increasing your stopping distance and the likelihood of an accident.

2. Brake Assist

Working in tandem with ABS and EBD is yet another feature called Brake Assist (BA). To review, ABS stops the wheels from locking up and EBD sends the right pressure to the front and back. BA ensures enough brake pressure is sent to trigger both systems. After all, both ABS and EBD are designed to work when strong brake pressure applied. Any less and it could make normal driving very uncomfortable. Several studies have shown that most drivers don’t apply enough brake pressure in the first place. BA determines if you pressed the pedal calmly or in panic. If it detects a panic stop, it boosts the pressure, activating both ABS and EBD so you can stop faster and more safely.

Brake Assist

Feels like…

The only downside to Brake Assist systems is they make brake pedals feel heavy and a little numb. This is because a sensor at the pedal constantly monitors each press to determine if it is a normal stop or a panic stop. It will feel normal in most conditions. In a panic stop however, the sudden surge of force on the pedal is all the system needs to get into action. Even before you’ve fully pressed on the brake pedal, the system fully depresses the pedal for you. You’ll notice that the pedal will have sank deeper and faster than you commanded it to. Just like EBD, there’s no indicator lamp for brake assist. It simply works silently in the background.

What to do…

This activity may lead some to think that their brakes are losing fluid or malfunctioning. The truth of the matter is, the car had already applied the full pressure of the brake pedal for you, activating both ABS and EBD in that split second. Don’t think or worry too much about not applying enough pressure to trigger these systems. Brake Assist is designed to worry about that for you. If it’s equipped in your car, you’re good. Your actions in a state of panic are all it needs to activate.

3. Traction and Stability Control

Turning is often a simple operation, but when combined with speed and emergency braking, can turn dangerous in an instant. Too much speed or too sharp a steering angle can easily lead to an accident. It’s bad enough that your mind is racing during an incident like this, that’s why Traction and Stability Control continuously monitor where the vehicle is pointing, your steering angle and each individual wheel’s speed for you. During a loss of control, it makes adjustments by independently applying the brake on individual wheels to make the turn at the safest possible speed and as close to the angle as intended. This keeps the car from spinning its wheels or sliding uncontrollably, especially when it is unintentional and in a panic situation.

Stability Control is also known by other names like Electronic Stability Control (ESP), Vehicle Stability Control (VSC), Dynamic Stability Control (DSC) and the like. Traction Control can also be called Traction Control System (TCS), Electronic Trottle Control (ETC) or Dynamic Traction Control (DTC). Regardless of the name, the purpose is still the same.

Traction Control

Feels like…

Traction and Stability Control make most of the adjustments for you. When a car loses stability, all sorts of feelings will flood your senses, like the back sliding out, the driving wheels clawing for grip and that sinking feeling you’ve done something wrong all within a split second. A split second later and the car detects you’ve lost control or traction, cuts power from the throttle and brakes the appropriate wheel to bring the car back under your control. On the instrument cluser, you’ll see the indicator for Stability or Traction Control blinking, telling you it’s working.

What to do…

The main thing you need to worry about is keeping the wheel pointed in the direction you want to go. Don’t worry about stepping on the gas or brake to correct the car. The vehicle will make the necessary corrections for you. Unless you’ve been educated by a licensed professional and are well aware of the lives you are placing at risk. Do not, under any circumstance, turn these systems off. A light will always come on in the dashboard if any of them are turned off. Some cars even feature a two-stage safety net to prevent you from turning it off completely. Naturally, the second stage is far more lenient, should you want to play around.

6. SRS Airbags

The Supplemental Restraint System (SRS) Airbag comes into play in the event of an impact. Airbags are called supplemental because seatbelts are still the first line of defense. Seatbelts keep you in the proper place to allow the airbags to slow down a passenger’s forward motion to minimize injuries during a crash. Without seatbelts on, you could slide under the wheel, to the side or a number of other directions that would make the airbag ineffective.

Airbags have sensors located in the front corner of the vehicle. In a strong enough impact, it sends signals to the crash sensor module. This ignites nitrogen, expanding and filling the airbag in milliseconds. Once inflated, it provides a soft cushion for the driver or passenger during a crash. It prevents occupants slamming onto the steering wheel or dashboard with deadly force.

Side airbags, curtain airbags and even knee airbags are simply variations of the same idea placed in different parts of the car. Side and curtain airbags help in the event of side impacts, and keep debris from the side from entering the vehicle. Knee airbags, in turn, prevent the driver from slipping under the wheel and also leg injuries.

SRS

Important note

Even if a vehicle is equipped with up to 10 airbags, it doesn’t mean all of them will inflate at the same time. First of all, it depends on where the collision happened. Second, it depends on how hard the collision is. Airbags are powerful devices and can cause more harm than good if they inflate when not needed. Inflation only happens when there is a collision force equal to running into a brick wall at 16 to 24 km per hour. If it inflates at lower speeds, the force of the airbag would be enough to break your neck.

If the crash happens in front or behind, then only the front airbags may inflate. If it happens on the left, then only the left airbags may inflate and vice versa. A combination of them may also inflate in circumstances where the car is hit in front and from the side. Just because an airbag did not inflate, it doesn’t mean it’s not working. That portion of the vehicle simply determined that an inflated airbag would have caused more harm than good.

Feels like…

During an impact, the vehicle’s sudden deceleration causes the bodies of the occupants to fly forward. This triggers the crash sensor module to start the airbag's inflation system. Its two components: Sodium azide (NaN3) and potassium nitrate (KNO3) react to produce nitrogen gas. Hot blasts of nitrogen inflate the airbag and are vented out through strategically placed exhaust holes. This allows the airbag to inflate quickly and deflate slowly. By the time the passenger impacts the bag, it is already fully inflated to cushion their momentum. It all happens very fast, and will feel like being thrust into a pillow. The passengers, limbs may fly around wildly, but if they’re wearing a safety belt, it will all be contained within the car’s safety cell. By the time you’re aware of what happened, the bag has deflated and your head and body are safe and free from injury. You probably feel some slight pain in the chest and waist area because of the seatbelt suddenly tightening.

What to do…

The best thing you can do to prepare for this is simply buckle up, especially for passengers behind. This puts you in the most effective position for the airbag to work. Passengers behind have their own seatbelts and the seatback to protect them in an impact. After an accident, check yourself and the other occupants in the car for serious injuries. Check your surroundings and only remove your seatbelt once the area is clear. Do not attempt to drive a vehicle after the airbag has inflated. It is not as structurally sound and the airbag will inhibit your driving abilities.

Conclusion

With much more intimate knowledge of how these systems work, we hope that you gain a better appreciation for these systems and how they can truly save lives. Remember to always keep them on, especially when driving in public roads. Cars, after all, can still be quite unpredictable, especially when compounded with the various conditions found in the roads out there. Even the most experienced professional drivers and stuntmen make mistakes. So when driving, especially with passengers on board, it’s better to keep these driving aids on and save lives.

*Inigo Roces received the 2012 Henry Ford Award for 'Best Smart Technology Feature' for this article